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| author | Cao Jin <caoj.fnst@cn.fujitsu.com> | 2019-08-28 14:11:00 +0800 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2019-08-28 08:38:39 +0200 |
| commit | cbb1133b563a63901cf778220eb17e3ff1425aed (patch) | |
| tree | bdda67667c1c74c2af1530a581a49f77b98f3769 /arch/x86/include | |
| parent | 248d327ed7b6d3ebda2ac7b38482a306108bcd3e (diff) | |
| download | linux-stable-cbb1133b563a63901cf778220eb17e3ff1425aed.tar.gz linux-stable-cbb1133b563a63901cf778220eb17e3ff1425aed.tar.bz2 linux-stable-cbb1133b563a63901cf778220eb17e3ff1425aed.zip | |
x86/cpufeature: Explain the macro duplication
Explain the intent behind the duplication of the
BUILD_BUG_ON_ZERO(NCAPINTS != n)
check in *_MASK_CHECK and its immediate use in the *MASK_BIT_SET macros
too.
[ bp: Massage. ]
Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Cao Jin <caoj.fnst@cn.fujitsu.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nadav Amit <namit@vmware.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190828061100.27032-1-caoj.fnst@cn.fujitsu.com
Diffstat (limited to 'arch/x86/include')
| -rw-r--r-- | arch/x86/include/asm/cpufeature.h | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index 58acda503817..59bf91c57aa8 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -61,6 +61,13 @@ extern const char * const x86_bug_flags[NBUGINTS*32]; #define CHECK_BIT_IN_MASK_WORD(maskname, word, bit) \ (((bit)>>5)==(word) && (1UL<<((bit)&31) & maskname##word )) +/* + * {REQUIRED,DISABLED}_MASK_CHECK below may seem duplicated with the + * following BUILD_BUG_ON_ZERO() check but when NCAPINTS gets changed, all + * header macros which use NCAPINTS need to be changed. The duplicated macro + * use causes the compiler to issue errors for all headers so that all usage + * sites can be corrected. + */ #define REQUIRED_MASK_BIT_SET(feature_bit) \ ( CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK, 0, feature_bit) || \ CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK, 1, feature_bit) || \ |